Automatic control of two-speed gears in aircraft



May Z0, 1941. E. scHuLTz Erm.

AUTOMATIC CONTROL OF TWO-SPEED GEARS IN AIRCRAFT 3 Sheets-Sheet 2 Filed Aug. `23,` 1938 'May 20, 1941 E. scHULTz ErAL 2,242,374 l Y AUTOMATIC CONTROL TWO-SPEED GEARS IN AIRCRAFT 'Filed Aug'.` -25, 193s Y s sheets-sheet`s at J EEE@ b .w WM Nk @Ku .QSW

Patented May 20, 1941 AUTOMATIC CONTROL F TWO-.SPEED GEARS IN AIRCRAFT Erich Schultz and Friedrich Bielitz, Dessau, Germany, assgnors to Junkers Flugzeug-und- Motorenwerke Aktiengesellschaft, Dessau, Germany Application August 23, 1938,'ser1a1N0. 226,264 u In Germany September 11, 1937 i 8 Claims.

y Our invention relates to aero engines and more especially to means for controlling the .operation of engines supplied with compressed combustion air. It is an object of our invention to provide means whereby the quantity of compressedair fed to the engine, is varied automatically corresponding to the altitude a-t which the craft is "flying In view of the rapid drop of the specific gravityof the atmospheric air at higher altitudes the internal combustion engines serving for -the propulsion of aircraft must be supplied with varying quantities of pre-compressed air if .their performance shall remain equal at all altitudes. In;

accordance herewith the superchargers, preferablyrof the rotary blower type, serving to feed compressed air to the engine are required to adapt their `performance to diierent altitudes of flight. To this end the superchargers have been provided with change speed gears serving to chargerand, as al1-emergency reversal, the automatic throwing in of the lower performance in the case of unduly high speed of the engine such as may occur for instance during a nose dive, when an unduly Ahigh stressing of the supercharger rotor must be avoided. 'Ihe reversing device shallfurther be so designed that the automatic reversal is already brought about by a slight variation of the atmospheric air pressure', i. e. within small diierences of altitude, so that the charger is prevented from unnecessarily operating as altitude supercharger with high perchange the number of revolutions of the rotor which determine the performance of the supercharger. AIn order to avoid complicated design of the change speed gear, as a rule a two speed gear is used which enables the supercharger to operate up Ito a predetermined altitude at lower and beyond Ithat altitude at higher speed and with a corresponding variationof performance, acting in the first case as ground superchargerz in the second case as altitude supercharger.

ormance,

In accordance with these requirements the reversing device according to this invention is tted with a snap action shitting mechanism which is moved quickly from one to another end position under the action of an auxiliary force which is adjusted in dependency from the altitude (or also manually" or by other influences) and in so moving, adjusts means for reversing the supercharger gear. 'Ihe control of the auxiliary force adjusting the snap action shifting' mechanism requires only little energy and a short movement of a control member, such as a 4bellows-responding to variations of the density of the air.

Therefore such a control device is highly sensitive, responding already to very slight variations The present invention relates more particularly to means for reversing such a two speed gear connected with a supercharger, these reversing means being so designed that the reversing occurs very quickly'in order to avoid a protracted slip in the clutches-which couple the rotary part of the supercharger either with fthe 'low speed or with the high speed gear driven by the driving part (for instance the engine crankshaft), since such slip would be accompanied byan obnoxious heating up and wearing of 'fthe parts. It is an object of this invention to keep the clutches a1- ways perfectly operative or perfectly inoperative and to provide for the quickest possible transi-A tion from the Voperative to'the inoperative positionand vice versa, this being particularly important in view of the very high numbers ofV revolution of the superchargers. The same eii'ect of the density, so that the automatic'reversal ofv .the supercharger gear, which is controlled by the density of the air,- occurs approximately at the same altitude during a. climb as well as during a descent.

- AIn the drawings aixed to this specification and forming part thereof two embodiments of our invenhon are illustrated diagrammatically by way of example.

In the drawings Fig. 1 is a diagrammatic showing of a reversing device forthe supercharger gear, which is actuated by a mechanical auxiliary force, while Figs. 2 and 3 are similar views of a reversing device, actuated by hydraulic means, in -two` different positions.

shall also be obtained at all actuations of the reversing device, no matter for what purpose and by what influences this device is. actuated. Another object of,the invention is the provision of means for automatically reversing the gear at a predetermined altitude, the optional reversing from higher to lower perfomance of the super- Referring to the drawings and first to Fig. .1, I is the rotor of the supercharger, fixed on a sha ft 2 which is driven by an engine '(not shown) which drives the shaft 3. On the shaft3 are l ,loosely mounted twogears 4 and 5, each of which meshes with a gear 6 and l, respectively, iixed on the 'shaft 2,. 'Ihe gear coupls l, 6 and 5, 'I

have dierent ratios of speed-transmission. On

the' shaft 3 a clutch member 8 is mounted ior-- axial displacement, but secured against angular displacement. A Clutch member can be coupled with either one or the other gear 4 and 5 by means of friction cones 9 and I0, respectively, so that according to the position of 'the clutch member the rotor of the supercharger is driven at lower or higher speed. The clutch member 8 is shifted by means of a double-armed lever I2 `oscillating about a xed journal I3 and gripping with one end the ring I6 encircling the clutch member 8, while its other end I1 is linked to a longitudinally displaceable rod I8. On this rod act two pressure springs 2|., 22 arranged after the manner of a toggle lever, which according to whether they are forced to the left or the right, exert a thrust in the same direction on the rod I8. On this rod are further mounted coil springs 23, 24 and stops 25, 26 arranged to be displaced in different directions, which coact with the cams 21 and 28 mounted on axles 29 and 30, respectively, which also carryI gear wheels 3| and 32 fixed to the cams 21 and 28, respectively and between which is located a worm 33 mounted on a shaft 34 which is connected by means of a Cardan joint 35 with the permanently rotating driving shaft 36, while its free end is connected by means of a sleeve 31 and link 38 to the pivot point 39 of a double-armed lever 40. One end 4| of this lever is connected by means of a link 43 to a bellows 44 acted upon by the atmospheric pressure. Its other end 42 is connected by means of the rod 45 to a. centrifugal governor 46, the spindle 41 of which is coupled with the propeller engine. The centrifugal governor is so constructed that the tension of its spring 48 is overcome only if the propeller engine rotates at unduly high speed. Therefore during normal operation the hinge point 42 remains stationary. A'hand lever 52 hinged about a fixed point 5| can be made to act on the rod 45 and is held in any predetermined posi'tion by means of the notches 53 and pawl 54.

This device operats as follows:

Owing to the instability of the extended position of the compression springs 2|, 22 arranged after the manner of-a toggle lever, the rod I8 will always take up either one or the other of two end positions, so that the clutch member 8 will be coupled either with the gear 4 of the lower step 4, 6 or withthe gear 5 of the' higher step 5, 1. In the position shown in the drawings the lower step 4, 6 is thrown in, and the 'parts are set for operation as ground supercharger.

. When climbing to higher altitudes, the bellows 44 will expand in proportion to the dropping air pressure and will rock the lever about the pivot point 42, thereby also rocking shaft 34 carrying the worm into engagement with the worm wheel 3| and setting this'wheel and the cams 21 rotating in the direction of the arrow a. A cam 21 striking the stop 25 will shift this stop against the action of spring 23, until the com' pression of this spring can counteract the force of springs 2|, 2 2 and throw the shaft I8 into the other end position with the springs 2|, 22 extending in the position shown in dotted lines. By this 4movement of the shaft the vlever I2 is caused'to quickly shift the clutch member 8 to pressed and the lever 40 and shaft 34 to be rocked in opposite position, wherein the worm33 is carried into engagement with the wheel 32, which is now rotated in the direction of arrow b together with the cams 2 8. One of the cams meeting stop 26, which was shifted farther to the left, will cause this latter to compress its spring 24 until it is able to overcome the resistance offered by the springs 2|,k 22, whereupon the rod I8. is forced back of a sudden into the position shown in the drawings, in whichv the lower step 4, 6 of the power transmission gearing is thrown in. If with the higher gearing in operation the speed of the propeller engine should rise unduly. the governor 46 Will come into action, which counter to the action of the spring 48 will pull the rod 45 to the right, whereby the lever 40 will be rocked to the right about the pivot point 4I, rocking the shaft 34 so that-the worm 33 ls brought into engagement with wheel 32 which will now throw in the lower step 4, 6, as described above. Obviously this reversal of the gear may also be effected manually by means of the lever 52, which,'on being rocked to the left in the sense y of the arrow c, shifts the rod 45 to the right.

The worm 33 and wheels 3|, 32 might also be replaced by other alternately operative means such as friction wheel gearings, friction clutches etc. I

In order to guarantee a quick' engagement of the worm 33`with one or the other wheel 3|, 32, another spring toggle similar to 2|, 22 might be inserted in theeconnection of the rod 43 and lever 40 with the worm gear.

In the reversing gear operated by hydraulic means, which is shown in Figs. 2 and 3, the clutch of the two speed gear is 'reversed by means of an oscillatory vane piston 6| arranged in a closed casing 60 and connected by means of a lever arm 62 with a system of rods 63 leading to the clutch (not shown). Two pipes 65 and 66 leading to the interior of the casing 60, however on opposite sides of the vane 6|, serve for controlling the flow of the pressure liquid. These pipes lead to a control case 61 formed with an axial bore 48, in which a control slide 69 can be reciprocated.

l With the bore 68 communicate three conduits 1l,

1I, 12, the middle one (10) communicating with the pressure side, the two others (1|, 12) with the suction side of a permanently rotating gear pump 15, which places the liquid under pressure. The piston or slide 89 is formed with three circumferential grooves 80, 8|, 82, which are so arranged that in all positions of the piston slide the conduit 10 communicates with the groove 89, conduit 1I with groove 8| and conduit 12 with groove 82. On the other hand the pipes 66 and 66 end in .the bore 68 in such position that they communicate in one end position' of the piston slide, shown in Fig. 2, with the grooves 8|, I6, in the other end position (Fig. 3) with the grooves 80 and 82. In the part formed with the groove 80 the piston slide is formed with a radially extending bore 11, which communicates by means of a narrow haxial bore'18 with the part 85 of the bore 68 which adjoins the bottom end face 19 of the piston slide. This space 85 is separated by a partition 81, formed with a bore 86, from Aa space 89, which permanently communicates withthe suction side of pump 15. With the bore 86 coacts a valve 8| mounted on a rod 82, which extends acrossthe wall |13,` being packed therecan be adjusted within certain limits by means of an adjusting device (set screw) 91.

At the other end the bore 68 merges into a chamber |00, which permanently communicates by way of a conduit I| with the suction side of pump lI5. The lateral wall of this' chamber is formed about in the middle with projections |02 oftriangular crosssection. The widenedl part, extending into the chamber |00, of the con'- trol piston is formed with a radial bore |03, in which are arranged two balls |04, which are permanently forced towards the outside by a spring inserted between them. The balls |04 rest against the projections |02. In the direction of movement of the piston slide 69 the slide is acted upon, from without, by a yprecompressed coil spring I06, which abuts against'the casing 61, tending to force the piston slide downwardly. ,A From the chamber `85 a conduit |08 leads to a casing |09, in which a piston slide |I0 is arranged for axial reciprocation, a conduit III leading back to the suction side of the pump prevents the clutch 'member of the 'change speed I pipe-ss and acispn the vane 6| in' the direction where the vaneis turned in the sense of the arrow y (Fig. 2), until the vane has reached the end position shown inFig. 3. At the same timeA the vane 6I acts on the rod 63 leadingl to-the change speed gear, which is adjusted tothe position cor- I.

responding to 'the higher speed, so thatno'w the supercharger operates-at the higher speed, i. e'. as

altitude supercharger.- Thesnap action mechanism formed by the projections |02, the balls |04 and the springl |05 provides for a quick reversal of the 1iquid inlet and outlet to the'means sb, si for adjusting the'reversing gear.' `In ccnsequence thereof the clutchmember of the change speed f' gearpasses quickly from one to the other. end position. The snap action mechanism, which can take up only one on thel other. end position,

. gear from' lstopping in any position other than the through the pipe 66'to the groove 62 and further 15.. On one side of .the slide IIO acts apressure spring II2, on the'other side the rod I|4 of a f centrifugal governor II5, which is driven by the propeller engine. In the normalv position shown in the drawings the slide I.I0 shuts off the inlet |08. It is formed with a circumferential groove II6 which communicates with the conduit III and, on the slide being shifted to the left, sets the conduits II I and |08 in communication. In a branch pipe of conduit |06 -is inserted a manually operable cock III, from which another branch line II8 leads to the line III and to the, suction side of the pump.

Fig. 2 illustrates the position of the parts corresponding to flight in air of higher specific gravity, in which the supercharger operates .withA compressed-and the valve 9I thus `uncovers the bore 86 so lthat the pressure uid entering the chamber 85 through the narrow'bore 18 can ow through bore 86 and chamber 88 into the conduit 89. By way of boreA 'I8 the conduits |08 and Ii 9 are also in communication with -the pressure pipe 10. Aslong, however, as the control members IIO and II1 are in the position shown in Fig. 2, they do not iniiuence the operation to .bedescribed hereinafter..

When the aircraft climbs to higher altitudes,

ythe bellows 94 will expanda'nd shift the valve 9| to cover and close the conduit 86. This results in a rise of pressure in the chamber 85 and as soon asthe pressure exceeds-the predetermined tension of the spring |06, the` slide 69 is shifted in' the direction ofthe arrow x. The two balls |04' end positions. 'I'he liquid displaced from the casing 60 on the vane' 6I beingV turned -flows through conduit 'I2 pump 15.

When the craft descends again, the bellows 94 is compressed'again, and the valve 9|' now uncovers the bore 86, wherebyfthe pressurein the 'chamber belowthe slide '69 is reduced. As soon as A this pressure has dropped suiciently, tne spring |06 under tension shifts the slide 69'downwardly, ,the snap action mechanism |02, |04, |05;

jumping back into its initial-position and causing the slide 69 tobe jerked into its lower end positionaccording to- Fig. 2. The pressure iluid ilowing from'the'conduit 10 towards the slide is now once more conducted through conduit 66 'to the vane casing 60, forcing the vane 6| l into the position shown in Fig.- 2, in which the supert elfected for instance, in'. the case of an unduly' high speed of the propeller engine, by the cen-` participate in this movementand at the same time also move in thejtransverse direction while remaining in contact with theedge of the projections '|02, The springs |05 and |06 are so organized that the forces opposed by them to the movement of the slide 69 and theballs |04 in the direction a: 'drop as the movement proceeds. Therefore, when the pressure acting on the slide 69 in the chamber 85 has -l'xecome high enough to displace the slide, it will, owing to this organization of the slide, cause it to, change over into the other end position' (shown in Fig. 3) with a jerk. The pressure liquid owing through the conduit I8 into the groove 80 now reaches the charger operates at the lower speed.

When the device is set for operation as altitude .supercharger (at high speed) according to Fig. 3, a reversal for operation atlow'er'speed can'also vbe broughtabout at any time within the range oflower air densitynj'In order to attain this, it is only necessary to reducethe pressure in the chamber 85 below the piston slide. This may be trifugal governor II5 so adjusting the slide IIO, that the conduit I I8, by way of its groove |I6,

-entei's into direct -communication with the pressure conduit I I I,-orby the valve I I1 being opened manually. All this is shown in Fig. 3.

While in the embodiment of Fig. 1 'the adjusting of the snap action mechanism' as well as the control of' `the 'clutch member are effected by` mechanical means, in the embodiment of Figs. 2 and 3. hydraulic means are provided for setting the snap action mechanism as Well as the clutch member. According to the invention these modes of operation may also be combined in a different manner. Thus a snap action mechanism adjustable by hydraulic means may be combined Y with a mechanically controlled clutch member, or a mechanical snap action mechanism with a clutch member controlled by hydraulic means. In the device of Figs. 2 and 3 it is further possible .to arrange'a hydraulically or mechanically adjustable snap action mechanism separately from the plston slide. Instead of actuating vthis mechanism or the clutch mem-ber by hydraulic means' also electrical'means may be provided for the same purpose, and the pressure liquid might also be replaced by a gas under pressure.

" Various changes may be made in the :details back to thesuction side ofthe I disclosed in the foregoing` specificationwithout departing from the invention o r sacricing the -advantages thereof.

We claim: 4 1. In combination with an aircraft engine supercharger having a change speedtransmission anda clutch therefor, clutch control means for ing means comprising a pivotally mounted rotatable shaft, means for transmitting rotations of said shaft into limited linear movement of said mechanism, and means for pivoting said shaft into engagement with said transmitting means.

4. In the combination of claim 1, said mechanism comprising a linearly movable rod having ,stops.thereon, and said actuating means comprising two rotatable cam members adapted to engage said stops for moving said rod, a rotatable shaft, and means for bringing said shaft into acrtuating engagement With one or the other of said cam members.

5. Inthe combination of claim 1, said mechanism comprising a hydraulic piston, and said actuating means comprising a pump, a valve, conduit means connecting said pump and valve to said` piston, and means for actuating said valve by fluid pressure from said pump.

6. In the combinationl of claim 1, said mechanism comprising a hydraulic piston, and said actuatin'g means comprising a pump, a valve, conduit means connecting said pump and valve to said piston, saidvalve including a fluid chamber at one end thereof and snap action spring'means at the other end thereof, and means for actuating said valve by producing fluid pressure in said chamberfrom said pump.,

7. In the combination of claim 1, said mechanisrn comprising a, vane piston, and said actuating means comprising a iiuid circulation system for said piston and including a iluid pump and a valve, and means for operating said valve to reverse the flow of fluid in said system.

8. In combination with an engine supercharger having a change speed transmission, clutch control means for said transmission-comprising a snap action shifting mechanism connected to said clutch, iirst means responsive to changes in baro- I metric pressure for actuating said'mechanism, and second means responsive to changes in engine speed for actuating said mechanism.

ERICH SCHULTZ. FRIEDRICH BIELITZ. 

